ghost_bros pretty much summed my toughts! Really charming, nice platforming mechanics, and neat mist animation! Also the music was a really good fit.
I too got very stuck on the second level and had to refer to the comments to beat it. It's a really neat idea!! But I think the issue is that the Narrator's clue is too vague. Even if the player is questioning whether or not the narrator is telling the truth, the sign doesn't really hint at what the narrator wants the player to do.
Perhaps a clue like "Jump into the deep ominous darkness" would be a bit better for that one :)
The level with the ability to switch between Leah and the main player though... that one I was unable to figure out even with the hint you gave Korlagwen. I kinda picked up on the idea of jumping through walls but wasn't really clear on what to do with it...
Overall, the game is very creative and has so many unique mechanics, but I think because of this combined with the unreliable narrator bit, I think the learning curve is a bit too steep for new players. Some things I think could help flatten that out a bit (You probably only have to add one of these, adding all would make the game too easy, and we still want a challenge! :P )
1) Adding more narrator clues throughout. Maybe they can appear after a certian number of deaths. Would also be a great way to see more of the narrator in action.
2) Add a checkpoint or two on some of the more spread out levels like the one with the 3 switches.
3) Make some quick gifs of yourself beating the parts that gave players trouble and put them on the itch page! Simultaneously works as a preview to the game and a mini spoiler free guide! :D
Hope these suggestions help you!
-Sasha